[llvm] r190665 - AArch64: use RegisterOperand for NEON registers.

[Tim Northover]

> AArch64: use RegisterOperand for NEON registers.

This seems to have broken the ASAN bot.
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap.

I think it's non-determinism due to TableGen's AsmMatcher sorting by
pointer and I'm tracking it down. But if anyone gets annoyed feel free
to revert the patch until I can put it in place with a fixed TableGen.

Tim.